WASHINGTON (CNN) --U.S. officials Tuesday added to the pressure on Syria, accusing Damascus of allowing the former head of Saddam Hussein's feared intelligence service to enter the country.

Secretary of State Colin Powell admitted Washington has concerns about Syria, which the United States has accused of harboring deposed Iraqi leaders and attempting to develop weapons of mass destruction.

But he added that the Bush administration has "no list" of U.S. enemies in line for military action.

During the past week U.S. diplomatic pressure on Syria has been stepped up with the most powerful figures in the administration, including Bush, publicly criticizing Syria and threatening sanctions.

U.S. officials said Tuesday Farouk Hijazi, ex-head of Saddam's Mukhabarat intelligence service, had arrived in Syria from Tunisia where he had been serving as Iraq's ambassador at the start of the war.

Hijazi is suspected of involvement in an unsuccessful plot by Iraqi intelligence to kill former President George Bush in Kuwait in 1993 after he had left office.

Powell said Tuesday the administration has no plans to attack any other country, "either for the purpose of overthrowing their leadership or for the purpose of imposing democratic values."

"Iraq was a unique case," Powell told reporters at the Foreign Press Center in Washington.

"It wasn't just a matter of a dictator being there, it was a dictator terrorizing his people ... (and) beyond that, invading his neighbors, threatening the whole world with weapons of mass destruction and supporting terrorist activities."

Saddam Hussein's government ignored "the will of the international community that told him to get rid of these weapons for a period of 12 years," Powell said.

He added: "We are concerned about Syria's development of (weapons of mass destruction), we are concerned about Syria's continuing support of terrorist organizations and in recent weeks we have been concerned about the flow of material across the Syrian border into Iraq, as well as the flow of individuals back and forth.

"We have concerns, which we have expressed rather directly and forcefully to the Syrians, over the fact that some Iraqi officials who are guilty of crimes -- or at least strongly suspected of crimes -- may be seeking haven in Syria. We don't believe Syria should find this in their interest."

Syria's deputy ambassador to the United States on Tuesday cautioned that the United States is starting to look like a country "that wants to attack one small country after another."

"Please be careful about what is going on," Imad Moustapha said on CNN's "American Morning." "This is not an easy game. It's not something to play with."

Accusations, but little evidence

On Sunday Bush warned Syria against harboring Saddam loyalists, and said U.S. officials "believe there are chemical weapons in Syria." (Full Story)

Defense Secretary Donald Rumsfeld has said intelligence shows Syria has allowed its citizens and others to cross the border into Iraq armed with weapons and carrying leaflets indicating rewards are available for killing Americans and members of the coalition. (Full story)

But so far U.S. officials have not provided much public evidence to support its accusations against Syria.

They said there are indications Syria allowed members of the militant Hezbollah into Iraq through Syria during the war, and Jaffar al Jaffar, the top Iraqi scientist now in U.S. hands in a Persian Gulf country, escaped from Iraq to Syria.

But U.S. officials also said that senior Iraqi regime officials are using false identity papers and back roads to try to get out of Iraq at various points along its 376-mile (605 km) border with Syria.

One official said the size of the border may prevent the Syrian government from knowing exactly who is in the country.

Diplomatic sources said there is little information to support the U.S. claim that Syria is harboring former Iraqi regime leaders.

There also appears to be some difference of interpretation between various U.S. agencies tracking senior Iraqi officials, U.S. officials told CNN. Pentagon officials are angered at intelligence suggesting some senior Iraqis may be escaping into Syria.

Also, State Department and intelligence agency officials remember Syria's help in the war on terrorism immediately after the September 11 terrorist attacks, and expect there will be a need to work with Syria in the future.

On the issue of chemical weapons, however, the diplomatic sources who spoke to CNN believe Syria is guilty.

When asked Tuesday if Syria would allow third-party weapons inspectors into the country to look for weapons of mass destruction, Moustapha turned the tables, asking whether the White House would send inspectors to Israel.

"Let me be very clear about this: Syria has always been calling for the international community to rid the Middle East from all weapons of mass destruction," he said.